Hot & Cold Composting In The Subacrctic

We have been fairly successful at producing our own compost in Alaska and want to share our methods and techniques.  Composting is the process of breaking down organic materials into compost, typically for use in gardening applications.  Compost is great for enriching soil with natural nutrients that will help plants grow better.

The Two Types Of Composting:

There are two types of composting that are largely recognized.  These are cold-composting processes and hot-composting processes.

Cold composting should be pretty familiar to most people.  It’s fairly well known that organic matter will break down eventually and return to soil.  Any time you see a rotten log on the ground, that’s effectively the cold composting process in action.   When we intentionally cold compost, we essentially pile up organic materials and allow this lengthy process to happen.  Bacteria and microbes will eventually invade the pile and slowly break down the organic materials into compost.  It can take months to years to get everything to fully break down, but eventually, you’ll be left with compost.  What’s great about cold composting is there are no rules or guidelines to follow.  If it’s organic, it will break down into compost eventually.

With hot composting, there are a few more specifics you have to follow.  When an ideal ratio of “green” and “brown” materials are put together, it creates a perfect environment for the bacteria and microbes.  When these thrive, the microbe and bacteria populations explode and you can get an extremely fast break down of materials.  Typically, you see a crazy increase in temperatures – up to 160 degrees Fahrenheit – thus the term hot composting.  Using hot composting methods, you can easily get finished compost in a matter of weeks to months.

What’s This About Green And Brown Materials?

When we talk about hot composting, the ratio of green and brown materials are important.  So is understanding what these two materials are.

Effectively, green materials are high in nitrogen, whereas brown materials are high in carbon.  These terms still don’t clarify the concept, though.  Fortunately, there are some general guidelines for these:

  • Green Materials
    • Food scraps
    • Grass clippings/weeds
    • Coffee grounds/tea leaves
    • Manure
    • Most garden waste
  • Brown Materials
    • Leaves
    • Sawdust
    • Wood chips
    • Straw/hay
    • Newspaper & cardboard
    • Spruce/Pine needles & cones
    • Wood ash

When we talk about the “ideal” ratio of green to brown materials for hot composting, we’re talking about the general amount of each type.  Ideally, you want about 3-4 parts of brown materials for every 1 part of green materials.  Put another way, the hot compost pile should be about 75% brown materials and 25% green materials.  This isn’t a perfect science, but the key is more brown material than green material.

Our Adventure Into Sub-Arctic Composting:

Some of our early research into composting indicated that cold-composting was really the only viable option in the interior of Alaska.  This made some sense, but we’re also not the type of people that accept anyone’s advice as gospel.

We have been doing some hot composting experiments over the last couple years.  As it turns out, the cold composting advice was completely wrong.  It’s very easy to get hot composting to work here in Fairbanks, at least over the summer and shoulder seasons.

The best option that we’ve found thus far has been something like a hybrid approach of the two techniques.  We use hot composting over the summer and then leave our piles over the winter for a good cold composting.  Using these techniques, we have been able to get a very rapid production of compost.  We aren’t waiting years for the process to break down the materials, either.

Getting A Compost Pile (Or Four) Going:

A compost pile can be as simple as a pile of materials somewhere on your property.  Some people build special containers for their compost piles, mostly for the purposes of neatly containing it.  There are many options available – from dedicated bins to DIY solutions to tumbling composters.

Composting can take some time, so it’s advantageous to have more than one compost pile.  This allows you to keep the primary stages of hot composting separate from one another.  These three stages are the initial materials when added to the compost pile, semi-composted materials and finished compost.

For us, we knew we had a fairly large amount of materials we’d be expecting to compost each year.  We also wanted to produce a fairly large amount of compost, too.  So, that meant that for our purposes, we had to look at something both cost effective and provided for a decent size of composting capacity.  This ruled out most of the more expensive tumbling compost bins, for us anyway.

The GeoBin Composting Solution:

We assessed the various compost bin solutions out there.  We settled on the GeoBin solution.

Patrick over at OYR Frugal & Sustainable Organic Gardening really turned us onto them.  He’s a great cold climate gardening YouTuber that we’ve been watching for years!

While DIY options were attractive to us, the lumber costs and construction time were a factor.  I don’t know if you’ve stabbed at chicken wire bins with a pitchfork, but I have, and the chicken wire compost bin was a no go for me.

Also, the GeoBin solution was infinitely more scalable.  For $35, we could easily add another 216 gallons of compost storage space at any time.

The GeoBin is both relatively inexpensive and also very efficient at composting.  The design promotes high air circulation within the compost pile.  It’s also really easy to work with the solution.  Setting up the piles were really easy to do.  We installed four fence posts in the ground and wrapped the GeoBin around them.  This provided excellent stability of the GeoBin, whether it was full or not.

At first, we weren’t sure how well the hot composting process was going to do.  After an initial trial of one of them, we found our hot composting techniques to be wildly successful.  It was then we pulled the trigger on two more.  And then one more.  We were really glad we went with the modular approach of the GeoBin compared to a DIY solution.

Our GeoBin Composting Bins





This is an image of the four GeoBins that we installed. This configuration allows for a lot of flexibility and the production of a lot of compost every year.  One bin usually accepts new material, a second is used for maturing compost.  A third bin is reserved for when we turn the piles and the fourth is designed to store our compost long term.

Compost piles generally require occasionally turning of the organic materials to re-invigorate the composting process.  The GeoBins make this very easy as they can be easily opened up for access.  We typically open one of them and use a pitch fork to turn the materials into another bin.

It might have been less expensive to use chicken wire fence material or hardware cloth for our compost bins.  We knew we’d be opening up our bins quite frequently, so we were concerned about long term durability.  The heavy duty plastic found in the GeoBin will likely hold up for many more years compared to fence materials or hardware cloth.  Either way, though, both options would have worked.

Setting Your Property Up For Long Term Composting Success:

Most people that get into composting have an excess of green materials.  From grass clippings to garden clippings, green materials are almost always in excess.  If you recall the ratio for hot composting, you need a lot of brown materials.  We had to really think about where those brown materials were going to come from.  This is a very common problem for most people that get into hot composting.

While we do have access to cardboard and infinite amounts of junk mail, this wasn’t quite the ideal solution for us.  While we do have some deciduous Birch trees that provide some leaves, they weren’t in sufficient supply over the entire summer.  When we looked at our property, it was obvious we had access to a fair amount of wood.  From our firewood processing to the management of trees on our property, wood was the obvious choice of brown materials for us.

With composting, however, it’s less than ideal to throw chunks of bark and branches into your pile.  These materials in that form will break down very slowly.  You ideally need to get the wood into a manageable form, ideally chips, for a much more rapid decomposition process.

While we could have rented a wood chipper each year, it made more sense for us to buy a good wood chipper.  We were going into this composting process for the long term.  While owning equipment can be expensive, it also provides flexibility and does become less expensive than renting in the long term.

The wood chipper also solved some other problems for us.  We were accumulating a lot of birch bark from our firewood processing.  There are also countless piles of branches across our property that we’d like to clean up.  We had several trees we needed to fell and knew we’d have a lot of excess branches to get rid of.  Eventually, we’d like to manage the forested portion of our property, again providing countless branches that we could turn into compost.

The wood chipper allowed us to practice a greater degree of permaculture on our property and also created the supply of brown materials we needed for composting.

The Sub-Arctic Approach To Hot Composting:

With a sufficient supply of green and brown materials solved, we sought to establish our hot composting strategy.

We started out gathering the materials we had available.  We chipped up a bunch of our firewood bark and tree branches.  As the spring and summer moved on, more and more green materials became available.  For a large portion of our green materials, we started to bag our grass clippings for adding to the compost pile.  We layered our green materials and brown materials into the GeoBins, roughly 3-4 inches for each layer.  Then, we continued this layering of green and brown materials until the bin was full.

Within a couple of days, we had an active hot compost pile.  We easily saw 140 to 160 degree Fahrenheit temperatures in our compost pile.  When we uncovered the pile, we saw massive populations of microbes (typically white in color), so we knew it was working.  Within weeks, we were seeing the nitrogen rich green materials break down quite quickly.  The pile quickly became smaller and smaller.

When the pile’s temperature decreased to ambient temperatures, we know it is time to turn it.  We open the GeoBin and use a pitchfork to move the material into the next GeoBin.  This mixes everything up and reactivates the compost bin.  We also mix in more green materials and grass clippings to this mixed bin, offering more nitrogen material to break down.  We tend to mix the piles and infuse more nitrogen materials every few weeks throughout the summer.

One of the main disadvantages to using wood as your brown material is that breaks down slowly.  It’s a very good brown material, but infusing the pile with more green materials is essential to getting complete break down of the wood chips.  If we were using other brown materials, we might not need to re-infuse as much green material into the mix.

The Hot-Cold Hybrid Approach To Sub-Arctic Composting:

We continue the GeoBin layering and mixing process throughout the summer season.  It’s important to take advantage of the weather while you have it.  Eventually, though, the six month winter will settle in and we shift from hot composting to cold composting.

Right before winter, we use a home built compost sifter to separate the compost from the materials that still haven’t broken down.  This sifter is just some 2×4’s formed into a rectangle with 1/4 inch galvanized steel hardware cloth stapled to the bottom.  We built our sifter to fit over our wheelbarrow.

We scoop our mix of materials into the sifter and shake out the compost into our wheel barrow.  Material that doesn’t fit through the hardware cloth is returned to the GeoBin for further composting.  We usually try to mix in our garden cleanup and final yard cleanup materials in, again in layers.  The completed compost is returned to either storage pots or an available GeoBin for longer term storage.

The fully mixed GeoBins then proceed to sit for the winter.  We’ve found it worthwhile to again sift the material in the spring.  The winter long cold composting process is fairly efficient as there are high numbers of bacteria and microbes in the pile.

Occasionally, the moose stop in at the pile for a winter snack.  That’s just how it goes here in the north.

Producing Large Amounts Of Sub-Arctic Compost:

In 2019, we were able to produce around 150 gallons of finished compost using the above methods.  This was with four GeoBins, which represented almost 900 gallons of composting capacity.  While we don’t use them to full capacity currently, the four GeoBins are about the right size for our composting needs.

We think we might need a little bit more compost each year, for both our home gardens and community gardens.  We might add a trash can near the house that would easily allow us to compost scraps over the winter.  Additionally, we might start bringing our green materials in from our community garden as well.  Our community garden has several cold compost piles that we’ve historically used, but the resulting compost isn’t great because people throw a lot of weeds into the piles.

Speaking of weeds, we are planning to build a soil sterilizer this spring out of a 55 gallon drum we purchased last year.  This will allow us to sterilize our compost, killing off any weed (or vegetable) seeds we accidentally get into our compost.  This soil sterilizer will also be used to sterilize our soil that we re-use in our container gardens.

3 comments… add one
  • Bert Feb 29, 2020 @ 14:00

    Good article Jeff. I think I may purchase one or two of the geo bins for myself in Montana.

  • Timothy Apr 7, 2020 @ 14:36

    Thanks for the post. I would like to use willow/alder chips. What type/size chipper would you recommend?

    • Jeff Apr 7, 2020 @ 15:23

      You are welcome! I would suggest avoiding the very inexpensive (~$100) “Sun Joe” type chippers as they are under powered and somewhat flimsy. Beyond that, chippers are rated and priced typically by the engine size as well as the branch size they can handle. 2 or 3 inch varieties will fit most homeowner applications, we went with 3 inch as we have branches that large. It’s also nice to have the 2-in-1 chipper/shredder function for general yard debris. You can also rent chippers from your local equipment rental or home improvement store. Good luck and may you be swimming in compost!

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